No advertising sign or billboard of any character shall be permitted to be used, except that, upon buildings one sign per establishment may be permitted not larger than 25 square feet in area, constructed parallel to and not more than 12 inches from the building wall to which it is attached. No flashing or moving signs will be permitted. No such permitted signs shall project above the first story, and they shall be limited to displaying the name and the nature of the business for which such building is used. Illuminated signs shall be of a channel-lighting type. No illuminated sign shall, however, be erected without first submitting a sketch for approval prior to the issuance of a permit by the Building Inspector. All exterior illuminated signs must be extinguished daily at the closing time of the establishment or at 11:00 p.m., whichever is later, and must remain extinguished until 8:00 a.m. No illuminated sign shall be placed within the interior of any premises so that the same shall be nearer than five feet to any show window or exterior window. No such illuminated sign shall in any event be of a neon or flashing type. No sign of any type, whether temporary or permanent, shall be affixed to the interior or exterior of any show window or exterior window so as to cover more than 25% of the outside exposed surface of any such window. Signs which are permitted to be erected, installed or maintained shall be of rigid material and so affixed to the premises so as to prevent the same from moving, waving, flapping or turning.